1. Technical Field
The present invention relates generally to cellular wireless systems; and more particularly to the transmission of data communications in cellular wireless systems.
2. Related Art
Cellular wireless systems support wireless communication services in many populated areas of the world. While cellular wireless systems were initially constructed to service voice communications, they are now called upon to support data communications as well. The demand for data communication services has exploded with the acceptance and widespread use of the Internet. While data communications have historically been serviced via wired connections, wireless users are now demanding that their wireless units also support data communications. Many wireless subscribers now expect to be able to “surf” the Internet, access their email, and perform other data communication activities using their cellular phones, wireless personal data assistants, wirelessly linked notebook computers, and/or other wireless devices. The demand for wireless system data communications will only increase with time. Thus, wireless systems are currently being created/modified to service these burgeoning data communication demands.
Significant performance issues exist when using a wireless system to service data communications. Wireless systems were initially designed to service the well-defined requirements of voice communications. Generally speaking, voice communications require a sustained bandwidth over a period of several minutes. Data communications, on the other hand, have very different performance requirements. Data communications are typically bursty, discontinuous, and may require a relatively high bandwidth during data transfer, which may be very short (on the order of a few seconds). To understand the difficulties in servicing data communications within a wireless system, consider the structure and operation of a cellular wireless system.
Cellular wireless systems include a “network infrastructure” that wirelessly communicates with wireless subscriber units within a respective service coverage area. The network infrastructure typically includes a plurality of base stations dispersed throughout the service coverage area, each of which supports wireless communications within a respective cell (or set of sectors). The base stations couple to base station controllers (BSCs), with each BSC serving a plurality of base stations. Each BSC couples to a mobile switching center (MSC). Each BSC also typically directly or indirectly couples to the Internet.
In operation, a wireless subscriber unit communicates with one (or more) of the base stations. A BSC coupled to the serving base station routes voice communications between the MSC and the serving base station. The MSC routes the voice communication to another MSC or to the public switched telephone network (PSTN). BSCs route data communications between a servicing base station and a packet data network that may couple to the Internet.
The wireless link between the base station and the wireless subscriber unit is defined by one of a plurality of operating technologies and standards, e.g., AMPS, TDMA, CDMA, GSM, etc. These operating standards, as well as new 3G and 4G operating standards, define the manner in which the wireless link may be allocated, setup, serviced and torn down. These operating standards must set forth operations that will be satisfactory in servicing both voice and data communications. Each of these next generation systems will be called upon to support high-speed data communications.
In currently deployed digital cellular networks, e.g., 1xRTT networks, both voice and data communications are supported via wireless digital communications. Depending upon particular service provider criteria, base station resources within a cell/sector are divided between voice and data users. In most systems, the service provider desires to limit call blocking for voice users. To accomplish this goal, the number of Walsh codes and the amount of transmit power that may be allocated to data users is limited. 1xRTT systems support two types of forward links for data service, Fundamental Channels (FCHs) and Supplemental Channels (SCHs). FCHs provide the basic data service to data users. SCHs are bursty higher bandwidth channels that are rapidly allocated and deallocated as cell/sector conditions permit. A data user is “blocked” when it cannot be allocated a FCH, i.e., when sufficient data user resources are unavailable for such an allocation.
In order to address this undesirable operation, in 1xRTT systems, each base station is controlled to reserve a certain percentage of available data user resources for FCHs. One technique involves reserving a percentage of available forward link transmit power in a base station for FCHs. Another technique involves reserving Walsh codes for FCH allocation. However, neither of these techniques considers cell/sector loading and the unique needs of wireless subscriber units operating in such a cell/sector.
A need therefore exists for allocation of available data user cell/sector resources among data users to increase throughput but to minimize data user blocking.